At the Marine 2015 Conference in Rome in June, post doc Martin Kristoffersen from NTNU presented his research on X65 steel pipes subjected to combined stretching and bending. Here’s the abstract:

“Subsea pipelines are occasionally struck and hooked by objects such as anchors or trawl gear. The initial denting followed by a potential hooking and displacement of the pipeline, with a simultaneous increase in tensile axial forces due to this displacement, cause a complex load and deformation history. This study examines the effect of applying three different axial loads (zero, constant, and linearly increasing) to a pipe while simultaneously deforming it transversely. These three tests were repeated with an internal pressure of 100 bar, and all tests were recreated numerically by finite element simulations, the results of which were in good agreement with the experiments. Adding an axial load increased the pipe’s resistance to bending in terms of force-displacement, and the same can be said of including internal pressure.”